﻿EXTERNAL ANATOMY. NOSTRILS. 57 



completely concealed by a dense tuft of stiff setaceous 

 feathers : both these peculiarities may have something of 

 the same effect, though produced in a different manner 

 to what we have just stated; while the care with which 

 nature has defended the nostrils of these birds is for the 

 double purpose of preventing their being injured by the 

 claws of insects, and to exclude every particle of wood, 

 which the bird scatters about while perforating and 

 breaking into the tree where he knows his food lies 

 concealed. In proportion as birds partake both of a 

 vegetable and an insect diet, so are these bristles more 

 or less developed. In the robin, for instance, they are 

 short and feeble, intimating that its diet is only partially 

 insectivorous, or rather, that it seldom captures flying 

 insects : and such we know to be the fact. Proceeding 

 a step further, we find the bristles of the thrush and 

 blackbird altogether rudimentary, leading us to suppose 

 that, although they may occasionally eat insects, they 

 never capture them when upon the wing. Experience 

 confirms this theoretical inference, for every field natu- 

 ralist is fully aware that such is truly the fact. 



(56.) The different forms of the nostrils, no less than 

 their situation, deserve attention ; for in both these parti- 

 culars they assume many different appearances. In all 

 the birds of prey, they are situated nearly in the middle 

 of a naked and soft skin, called the cere, which covers 

 the base of both mandibles, and is probably connected 

 with the sense of smell. The cere, however, is not con- 

 fined to the rapacious tribes; for we find it, although 

 much smaller, in almost the whole of the parrot family, 

 whose food is entirely vegetable. No other land birds 

 possess this appendage ; nor can it be said to exist, under 

 the same form, in any other birds excepting some of the 

 rasorial orders: most of the cranes, herons, &c. have 

 the space between the eye and the bill naked and soft ; 

 but this is merely from the ordinary skin being destitute 

 of feathers. The nostrils are either placed, 1. at the 

 base of the lateral surface of the bill, as in the generality 



